The present invention relates to an absorption refrigerating machine, and more particularly, to an absorption refrigerating machine having a large pumping-up temperature difference and an absorption refrigerating machine suitable for low temperature generation of not more than 0.degree. C.
An example of an absorption refrigerating machine having a large pumping-up temperature difference and an absorption refrigerating machine capable of producing a low temperature under 0.degree. C., is disclosed in JP-A-7-139844. In this prior art, evaporators and absorbers are arranged in a two-stage manner so that the pumping-up temperature difference from the low temperature side to the high temperature side can be made large. And besides, an absorbent is mixed into a refrigerant to lower the solidifying point of the refrigerant. With this construction, the evaporation of the refrigerant becomes possible also in the temperature under 0.degree. C. and low temperature generation becomes possible.
In the construction disclosed in this prior art publication, since two sets of evaporators and absorbers are used, evaporation heat-transfer surface and absorption heat-transfer surface respectively become double. Therefore, the number of heat-transfer pipes or the number of heat-transfer plates increase, which leads to a disadvantage that the cost increases.
The above prior art publication also discloses an example in which one evaporator comprises a flash evaporator, and refrigerant, cooled by this evaporator, cools an absorber, and with this construction the number of heat-transfer pipes is reduced. In this case, however, the power of a refrigerant pump is increased.
And besides, although the concentration of mixed refrigerant is varied in accordance with the generating temperature, liquid refrigerant is caused to flow to a solution side without being evaporated, and therefore the refrigerant is used inefficiently. This leads to a disadvantage that the overall efficiency is lowered.